Use GW reparameterisations by default

[mj-will]

Currently GWFlowProposal will not use the included reparameterisations if reparameterisations=None. This means that running the sampler with the correct proposal doesn't guarantee the correct reparameterisations.

This PR adds an option to force FlowProposal or any class that inherits from it to use the default reparameterisations even if reparameterisations=None and adds an attribute that defines the default behaviour.

Changes

• Add attribute use_default_reparameterisations to FlowProposal this defaults to False and can be overridden by child classes.
• Add use_default_reparameterisations=None to the inputs of FlowProposal. When set to None the default for the class is used. Setting it to True or False overrides the default behaviour.

[codecov-commenter]

Codecov Report

Merging #129 (e0237dd) into main (81e810b) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #129   +/-   ##
=======================================
  Coverage   95.03%   95.04%           
=======================================
  Files          39       39           
  Lines        3628     3635    +7     
=======================================
+ Hits         3448     3455    +7     
  Misses        180      180           

Flag	Coverage Δ
unittests	95.04% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
nessai/gw/proposal.py	84.37% <100.00%> (+0.50%)	⬆️
nessai/proposal/flowproposal.py	97.51% <100.00%> (+0.02%)	⬆️

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